1. Field of the Invention
The present invention relates to a control apparatus for a vehicle, that has an inter-vehicle distance control unit, an engine stop-start unit, and a vehicle stop state maintenance unit.
2. Description of Related Art
An idle-stop technology in which the engine is stopped when the vehicle is stopped by the driver's operation of a brake pedal is known. In addition, there has been known a technology in which the stopped engine is started by the idle-stop technology when the driver's foot is moved away from the brake pedal. Both the technologies are collectively called idle-stop function, start & stop function, engine • automatically • start • stop function, or the like (hereinafter, simply referred to as “idle-stop function”).
In addition, there has been known a technology in which a traveling following a preceding vehicle with an inter-vehicle distance corresponding to vehicle speed is performed while the preceding vehicle is captured, and a traveling at a preset constant speed is performed if no preceding vehicle is captured, and which is referred to as constant-speed traveling • inter-vehicle distance control function and/or ACC (Adaptive Cruise Control) or the like (hereinafter, referred to as “inter-vehicle distance control function”). Moreover, a full vehicle speed range inter-vehicle distance control function in which the host vehicle is also stopped if the preceding vehicle is slowed down to stop and the host vehicle is also started if the preceding vehicle is started, is known as a mode of the inter-vehicle distance control function.
In addition, there has been known a technology in which the braking state of the vehicle is maintained even if the driver moves his foot away from the brake pedal after the vehicle has stopped, and which is called braking hold function and/or hill-start assistance (hereinafter, simply referred to as “vehicle stop maintenance function”), or the like. By this technology, the driver does not need to depress the brake pedal in the case of waiting for the traffic lights, etc., so the driver's fatigue can be alleviated.
By equipping the vehicle with the idle-stop function, the full vehicle speed range inter-vehicle distance control function, and the vehicle stop maintenance function, the idle-stop function is capable of stopping the engine after the host vehicle is stopped by the full vehicle speed range inter-vehicle distance control function (for example, refer to Japanese Patent Application Publication No. 2012-206593 (JP 2012-206593 A)). In JP 2012-206593 A, a cruise control system is disclosed, in which when the host vehicle is stopped by the full vehicle speed range inter-vehicle distance control function, a holding force for keeping the vehicle in the stop state is generated, and the engine of the host vehicle is automatically stopped when a condition to automatically stop the engine is satisfied.
However, if the vehicle equipped with the idle-stop function and the full vehicle speed range inter-vehicle distance control function is further equipped with the vehicle stop maintenance function, the driver may feel uncomfortable.
It will be explained below. As described in JP 2012-206593 A, in the case where the vehicle has been stopped by the full vehicle speed range inter-vehicle distance control function, stopping the engine by the idle-stop function helps to improve the fuel economy. In addition, by activating the vehicle stop maintenance function in the case where the vehicle has been stopped by the full vehicle speed range inter-vehicle distance control function, a braking force can be held during a period until the engine is started by the idle-stop function.
Therefore, in the vehicle equipped with the idle-stop function, the full vehicle speed range inter-vehicle distance control function and the vehicle stop maintenance function, it is deemed to be reasonable to take the activation of the vehicle stop maintenance function, in place of depression of the brake pedal by the driver, as an engine stop condition of the idle-stop function.
That is, the thus set vehicle operates as follows. The full vehicle speed range inter-vehicle distance control function is set (set to be active)→ the activation condition of the idle-stop function is changed to the activation of vehicle stop maintenance function→ the vehicle is stopped by the full vehicle speed range inter-vehicle distance control function→ the vehicle stop maintenance function is activated→ the engine is stopped by the idle-stop function. However, if the activation of vehicle stop maintenance function is used as the engine stop condition of the idle-stop function when the full vehicle speed range inter-vehicle distance control function is set, the following situations sometimes occur. Firstly, before the full vehicle speed range inter-vehicle distance control function is set by the driver, the brake pedal may be operated by the driver to slow down and stop the vehicle, however, the engine will not be stopped if a depression of the brake pedal with a predetermined depression force or above is not detected by the idle-stop function. Thus, it is possible for the driver to adjust according to his willing whether or not the engine is to be stopped by the idle-stop function.
However, if the full vehicle speed range inter-vehicle distance control function is set when the vehicle has been stopped and the engine is driving, the vehicle stop maintenance function is activated to stop the engine by the idle-stop function. Thus, in the case where the driver does not recognize that the setting of the full vehicle speed range inter-vehicle distance control function may become an activation switch of the idle-stop function, the driver may mistakenly think that the engine is stopped due to a malfunction (may feel uncomfortable).